WO2019176432A1 - Power reception device - Google Patents

Abstract

In order to perform an appropriate switching operation according to the state of current flowing through a coil of a power reception device, a power reception device 200 is provided with: a secondary coil L2; a resonance coil Lx and a resonance capacitor Cx which are connected to the secondary coil L2 and which constitute, along with the secondary coil L2, a resonance circuit having a prescribed resonance frequency; an AC current detection unit 230 that detects AC current i, which flows to the resonance circuit when the secondary coil L2 receives an AC magnetic field; a power conversion unit 250 that controls the AC current i by causing MOS transistors Q1, Q2 to separately execute switching operations; and a drive control unit 240 that controls the switching operations of the MOS transistors Q1, Q2. The drive control unit 240 changes timings of the switching operations of the MOS transistors Q1, Q2 on the basis of the AC current i detected by the AC current detection unit 230.

Description

Power receiving device

The present invention relates to a power receiving device used in wireless power feeding.

In recent years, in an electric vehicle or the like, a wireless power feeding system that feeds power wirelessly from a power transmitting device provided on the ground side to a power receiving device provided on the vehicle side is being realized. In such a wireless power feeding system, a wireless power feeding technique using magnetic field resonance or magnetic field induction has attracted attention. In magnetic field induction, a magnetic field (magnetic flux) is generated by flowing an alternating current through a coil provided in a ground-side power transmission device, and this magnetic field is received by a coil provided in a vehicle-side power receiving device to generate an alternating current. By doing so, wireless power feeding from the power transmitting device to the power receiving device is realized. On the other hand, magnetic resonance is the same as magnetic field induction in that a coil is provided in each of the power transmission device and the power reception device, but by matching the frequency of the current flowing in the coil of the power transmission device with the resonance frequency of the coil of the power reception device, Resonance is generated between the power transmission device and the power reception device. As a result, the coil of the power transmission device and the coil of the power reception device are magnetically coupled to achieve highly efficient wireless power feeding.

Regarding the wireless power feeding technology described above, the following Patent Document 1 is known. Patent Document 1 includes a power receiving coil that transmits and receives electric power by external magnetic coupling, a bridge circuit, and a smoothing capacitor, and a load is connected to both ends of the smoothing capacitor, and the bridge circuit includes a semiconductor switch and a diode in antiparallel. A power supply device including a plurality of connected switching arms and having a current detection means for detecting a current of a power receiving coil, a voltage detection means for detecting a voltage between DC terminals, and a control device is described. In this power feeding device, the control device determines that the AC inter-terminal voltage v is between the DC terminals only during a period in which the AC inter-terminal voltage v is equal to the front and rear around a point where the predetermined compensation period φ is shifted from each zero cross ZCP of the current i. Switching is performed so that the voltage Vo becomes a positive / negative voltage having a peak value, and becomes zero voltage in other periods, and the compensation period φ is set so that the period in which the AC terminal voltage v becomes zero voltage becomes the shortest.

Japanese Patent Laid-Open No. 2015-23658

In a wireless power feeding system used for an electric vehicle or the like, a combination of a power transmitting device and a power receiving device is not necessarily constant, and there are various combinations. Therefore, depending on the combination, high-efficiency magnetic field resonance cannot be used, and wireless power feeding by magnetic field induction or wireless power feeding in a state where magnetic field resonance and magnetic field induction are mixed may occur. In such a case, in the power supply device described in Patent Document 1, it is difficult to realize an appropriate switching operation according to the state of the current flowing through the power receiving coil, and thus there is room for improvement regarding the switching operation.

A power receiving device according to the present invention receives an AC magnetic field emitted from a primary coil installed on the ground side and is wirelessly fed, and is connected to a secondary coil and the secondary coil to have a predetermined resonance frequency. A resonant element comprising the secondary coil together with the secondary coil, an AC current detector for detecting an AC current flowing in the resonant circuit when the secondary coil receives the AC magnetic field, and a plurality of switching elements. And a power conversion unit that controls the alternating current by causing each of the plurality of switching elements to perform a switching operation, and a drive control unit that controls a switching operation of the plurality of switching elements, and the drive control unit includes: The timing of the switching operation is changed based on the alternating current detected by the alternating current detector.

According to the present invention, it is possible to realize an appropriate switching operation according to the state of the current flowing in the coil of the power receiving device.

1 is a diagram illustrating a configuration of a wireless power feeding system according to a first embodiment of the present invention. It is a figure which shows the structural example of the power receiving apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the processing flow of the wireless power feeding system which concerns on the 1st Embodiment of this invention. It is a figure which shows the processing flow of the drive control process in the power receiving apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing of switching operation | movement. It is a figure which shows the structure of the wireless electric power feeding system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structural example of the power receiving apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the processing flow of the drive control process in the power receiving apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the wireless electric power feeding system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structural example of the power receiving apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the processing flow of the drive control process in the power receiving apparatus which concerns on the 3rd Embodiment of this invention.

Hereinafter, embodiments of a power receiving device according to the present invention will be described with reference to the drawings.

-First embodiment-
FIG. 1 is a diagram showing a configuration of a wireless power feeding system 1 according to the first embodiment of the present invention. A wireless power feeding system 1 shown in FIG. 1 is used in wireless power feeding to a vehicle such as an electric vehicle, and includes a power transmission device 100 installed on the ground side in the vicinity of the vehicle and a power receiving device respectively mounted on the vehicle side. 200, a battery 300, and a load 400.

The power transmission device 100 includes a power transmission control unit 110, a communication unit 120, an AC power source 130, a power conversion unit 140, and a primary coil L1. The power transmission control unit 110 controls the power transmission apparatus 100 as a whole by controlling the operations of the communication unit 120 and the power conversion unit 140.

The communication unit 120 performs wireless communication with the communication unit 220 included in the power receiving device 200 under the control of the power transmission control unit 110. Various information necessary for wireless power feeding is exchanged between the power transmitting apparatus 100 and the power receiving apparatus 200 by wireless communication between the communication unit 120 and the communication unit 220. For example, information such as the frequency of the alternating current flowing through the primary coil L1, that is, the frequency of the alternating magnetic field emitted from the primary coil L1, is transmitted from the communication unit 120 to the communication unit 220. In addition, information such as the state of charge (SOC) and deterioration state of battery 300 and the allowable current during charging is transmitted from communication unit 220 to communication unit 120.

AC power supply 130 is a commercial power supply, for example, and supplies predetermined AC power to the power conversion unit 140. The power conversion unit 140 outputs an alternating current having a predetermined frequency and current value to the primary coil L <b> 1 using the alternating current power supplied from the alternating current power supply 130 under the control of the power transmission control unit 110. Primary coil L1 is installed on the ground side located under the vehicle, and emits an alternating magnetic field corresponding to the alternating current flowing from power conversion unit 140 toward the vehicle. Thereby, wireless power feeding to the vehicle is performed.

The power receiving apparatus 200 includes a power reception control unit 210, a communication unit 220, an alternating current detection unit 230, a drive control unit 240, a power conversion unit 250, a secondary coil L2, a resonance coil Lx, and a resonance capacitor Cx. The resonance coil Lx and the resonance capacitor Cx are connected to the secondary coil L2, and constitute a resonance circuit together with the secondary coil L2. The resonance frequency of the resonance circuit is determined according to the inductances of the secondary coil L2 and the resonance coil Lx and the capacitance value of the resonance capacitor Cx. Note that the resonant coil Lx and the resonant capacitor Cx may each be composed of a plurality of elements. Further, part or all of the resonance coil Lx may be substituted by the inductance of the secondary coil L2.

The power reception control unit 210 controls the power reception apparatus 200 as a whole by controlling the operations of the communication unit 220 and the drive control unit 240. The communication unit 220 performs wireless communication with the communication unit 120 included in the power transmission device 100 under the control of the power reception control unit 210, and stores various types of information as described above exchanged between the power transmission device 100 and the power reception device 200. Send and receive. Information such as the frequency of the alternating current flowing through the primary coil L1 received by the communication unit 220 is output from the communication unit 220 to the power reception control unit 210.

The alternating current detection unit 230 detects the alternating current flowing through the resonance circuit including the secondary coil L2 when the secondary coil L2 receives the alternating magnetic field emitted from the primary coil L1. Then, an AC voltage whose frequency and amplitude change according to the detected AC current is generated and output to the drive control unit 240. The drive control unit 240 can acquire the frequency and magnitude of the alternating current flowing through the resonance circuit based on the alternating voltage input from the alternating current detection unit 230.

The drive control unit 240 controls the switching operations of the plurality of switching elements included in the power conversion unit 250 under the control of the power reception control unit 210. At this time, the drive control unit 240 changes the timing of the switching operation of each switching element based on the alternating current flowing through the resonance circuit detected by the alternating current detection unit 230. A specific method for changing the timing of the switching operation will be described later.

The power conversion unit 250 has a plurality of switching elements, and controls the AC current flowing through the resonance circuit and rectifies by switching each of the plurality of switching elements, thereby converting AC power to DC power. Do. The power conversion unit 250 is connected to a chargeable / dischargeable battery 300, and the battery 300 is charged using DC power output from the power conversion unit 250. Note that a smoothing capacitor C0 for smoothing an input voltage to the battery 300 is connected between the power conversion unit 250 and the battery 300.

A load 400 is connected to the battery 300. The load 400 provides various functions related to the operation of the vehicle using the DC power charged in the battery 300. The load 400 includes, for example, an AC motor for driving a vehicle, an inverter that converts DC power of the battery 300 into AC power, and supplies the AC power to the AC motor.

Next, details of the power receiving apparatus 200 to which the present invention is applied in the wireless power feeding system 1 of FIG. 1 will be described. FIG. 2 is a diagram illustrating a configuration example of the power receiving device 200 according to the first embodiment of the present invention.

As shown in FIG. 2, the alternating current detection unit 230 is configured using, for example, a transformer Tr. When the magnetic flux generated by the alternating magnetic field emitted from the primary coil L1 is linked to the secondary coil L2, an electromotive force is generated in the secondary coil L2, and an alternating current i flows through the resonance circuit including the secondary coil L2.
When this alternating current i flows through the primary coil of the transformer Tr, an alternating voltage Vg whose frequency and amplitude change according to the alternating current i is generated at both ends of the secondary coil of the transformer Tr. Thereby, the alternating current detection part 230 can detect the alternating current i. Note that the AC current detection unit 230 may be configured by using a device other than the transformer Tr as long as the AC current i flowing through the resonance circuit can be detected.

The power conversion unit 250 includes two MOS transistors (MOSFETs) Q1 and Q2 connected in series. The MOS transistors Q1 and Q2 perform a switching operation for switching between the source and the drain from the conductive state to the disconnected state or from the disconnected state to the conductive state in accordance with the gate drive signal from the drive control unit 240. By this switching operation, the MOS transistor Q1 can function as an upper arm switching element, and the MOS transistor Q2 can function as a lower arm switching element. A resonance circuit including the secondary coil L2 is connected to the connection point O between the MOS transistors Q1 and Q2 and the source terminal of the MOS transistor Q2. Therefore, the AC current i flowing through the resonance circuit can be controlled and rectified by switching the MOS transistors Q1 and Q2 at appropriate timings.

2 exemplifies the power conversion unit 250 having a half-bridge configuration using two MOS transistors Q1 and Q2 as switching elements, but as a power conversion unit 250 having a full-bridge configuration using four MOS transistors as switching elements. Also good. In the following, an example of operation by the power converter 250 having the half-bridge configuration shown in FIG. 2 will be described, but the basic operation is the same even when the full-bridge configuration is used.

The drive control unit 240 includes a voltage acquisition unit 241, a comparison unit 242, a drive signal generation unit 243, and a gate drive circuit 244.

The voltage acquisition part 241 acquires the alternating voltage Vg output from the alternating current detection part 230 (transformer Tr), and outputs it to the comparison part 242.

The comparison unit 242 receives the AC voltage Vg acquired by the voltage acquisition unit 241 and a predetermined threshold voltage Vα. The threshold voltage Vα is a voltage for adjusting the phase of the gate drive signal output to the power converter 250, and the voltage value is set in advance according to the phase adjustment amount. The comparison unit 242 compares the input AC voltage Vg and the threshold voltage Vα, and outputs a phase signal Sp corresponding to the comparison result to the drive signal generation unit 243. The details of the comparison performed by the comparison unit 242 will be described later with reference to the processing flow of FIG.

In addition to the phase signal Sp from the comparison unit 242, the basic drive signal Sr from the power reception control unit 210 is input to the drive signal generation unit 243. The basic drive signal Sr is an AC signal that is output from the drive control unit 240 to the power conversion unit 250 and is a source of a gate drive signal that controls the switching operation of the MOS transistors Q1 and Q2, and the frequency thereof is the primary power transmission device 100. It is determined according to the frequency of the current flowing through the coil L1. Specifically, when the communication unit 220 receives information representing the frequency f of the alternating current flowing through the primary coil L1 of the power transmission device 100 from the communication unit 120, the communication unit 220 outputs the information to the power reception control unit 210. When the information on the frequency f is input from the communication unit 220, the power reception control unit 210 generates a basic drive signal Sr corresponding to the frequency f and outputs it to the drive control unit 240. The basic drive signal Sr is, for example, a combination of two rectangular waves corresponding to the MOS transistors Q1 and Q2, respectively, and has an H level corresponding to ON (conducting state) and an L level corresponding to OFF (disconnected state). Are alternately repeated at the frequency f. However, a predetermined protection period is provided between the H levels of the two rectangular waves so that the MOS transistors Q1 and Q2 are not turned on simultaneously.

The drive signal generation unit 243 generates a charge drive signal Sc in which the phase of the basic drive signal Sr input from the power reception control unit 210 is changed based on the phase signal Sp input from the comparison unit 242. Then, the generated charge drive signal Sc is output to the gate drive circuit 244. The details of the method for generating the charge drive signal Sc by the drive signal generation unit 243 will be described later with reference to the processing flow of FIG.

The gate drive circuit 244 outputs a gate drive signal based on the charge drive signal Sc input from the drive signal generation unit 243 to the gate terminals of the MOS transistors Q1 and Q2, respectively, and causes the MOS transistors Q1 and Q2 to perform a switching operation. Thus, in the power conversion unit 250, the MOS transistors Q1 and Q2 function as switching elements, respectively, and control of the alternating current i flowing in the resonance circuit according to the alternating magnetic field emitted from the primary coil L1, or the alternating current power to the direct current power. Conversion to

The power receiving device 200 of the present embodiment can charge the battery 300 by receiving wireless power feeding from the power transmitting device 100 by performing the operation described above.

Next, the flow of wireless power feeding using the wireless power feeding system 1 will be described. FIG. 3 is a diagram showing a processing flow of the wireless power feeding system 1 according to the first embodiment of the present invention. When the vehicle equipped with the power receiving device 200, the battery 300, and the load 400 is parked at a predetermined charging position, the processing flow of FIG.

In step S10, the ground-side power transmission device 100 issues a charge inquiry to the vehicle-side power reception device 200. Here, for example, charging is inquired by transmitting a predetermined communication message from the communication unit 120 of the power transmission device 100 to the communication unit 220 of the power reception device 200.

In step S20, the power receiving device 200 that has received the charge inquiry in step S10 notifies the power transmitting device 100 of the allowable current of the battery 300 during charging. At this time, the power receiving apparatus 200 determines the allowable current based on, for example, the charge state or deterioration state of the battery 300 measured in advance, and transmits information indicating the value of the allowable current from the communication unit 220 to the communication unit 120 of the power transmission apparatus 100. Send. Note that, when charging is unnecessary, the power receiving apparatus 200 may notify the power transmitting apparatus 100 to that effect. In this case, the process flow of FIG. 3 is complete | finished, without performing the process after step S30.

In step S30, the power transmission device 100 determines the amount of current and starts power transmission to the power reception device 200. At this time, the power transmitting apparatus 100 compares the output current value corresponding to the allowable current notified from the power receiving apparatus 200 in step S20 and its own rated current value, and selects the smaller one to determine the current amount. . Then, the power transmission control unit 110 controls the power conversion unit 140 to cause an alternating current corresponding to the determined current amount to flow through the primary coil L1, thereby generating an alternating magnetic field in the primary coil L1 and starting power transmission. At this time, by further transmitting information representing the frequency f of the alternating current flowing through the primary coil L1 from the communication unit 120 to the communication unit 220 of the power reception device 200, the power reception control unit 210 of the power reception device 200 sets the frequency f to It is preferable that the above-described basic drive signal Sr can be generated. Alternatively, the frequency f may be notified from the power transmitting apparatus 100 to the power receiving apparatus 200 when an inquiry for charging is made in step S10.

In step S40, the power receiving device 200 performs drive control processing of the power converter 250 according to the alternating current i that flows through the resonance circuit including the secondary coil L2 by receiving the alternating magnetic field emitted from the primary coil L1. Here, the drive control unit 240 performs the process shown in the process flow of FIG. 4, thereby performing drive control of the power conversion unit 250 according to the alternating current received from the power transmission device 100. Thereby, the battery 300 is charged in the constant current (CC) mode.
Note that the processing flow of FIG. 4 will be described later.

In step S50, the power receiving device 200 determines whether or not the state of charge (SOC) of the battery 300 has reached a predetermined value, for example, 80% or more. As a result, if the SOC is less than 80%, the drive control process of step S40 is repeated. If the SOC becomes 80% or more, the constant current mode is changed to the constant voltage (CV) mode and the process proceeds to step S60.

In step S60, the power receiving device 200 notifies the power transmitting device 100 of a charging current corresponding to the current state of charge of the battery 300. At this time, the power receiving apparatus 200 determines a charging current with a value smaller than the allowable current notified in step S20 based on the current charging state of the battery 300, and receives information indicating the value of the charging current from the communication unit 220. It transmits to the communication part 120 of the power transmission apparatus 100.

In step S70, the power receiving device 200 performs the same drive control process as in step S40, thereby charging the battery 300 in the constant voltage (CV) mode.

In step S80, the power receiving device 200 determines whether the state of charge (SOC) of the battery 300 has reached 100% of full charge. As a result, if the SOC is less than 100%, the process returns to step S60 to continue charging the battery 300, and if the SOC reaches 100%, the process proceeds to step S90.

In step S90, charging of the battery 300 is terminated. Here, for example, by transmitting a predetermined communication message from the communication unit 220 of the power receiving device 200 to the communication unit 120 of the power transmission device 100, the power transmission stop is instructed. In the power transmission device 100, power transmission is stopped by interrupting the energization of the primary coil L1 in response to the power transmission stop instruction. When the power transmission from the power transmission device 100 is stopped, the operation of the power conversion unit 250 in the power reception device 200 is stopped, thereby completing the charging of the battery 300.

When the charging of the battery 300 is finished in step S90, the processing flow of FIG. 3 is finished. Thereby, the wireless power supply of the wireless power supply system 1 is completed.

Next, the drive control process performed in steps S40 and S70 of FIG. 3 will be described. FIG. 4 is a diagram illustrating a processing flow of drive control processing in the power receiving device 200 according to the first embodiment of the present invention.

In step S110, the drive control unit 240 acquires the AC voltage Vg from the AC current detection unit 230. Here, the voltage acquisition unit 241 is used to acquire the AC voltage Vg corresponding to the AC current i flowing through the resonance circuit including the secondary coil L2, from the AC current detection unit 230 configured by the transformer Tr as shown in FIG. To do.

In step S120, the drive control unit 240 uses the comparison unit 242 to compare the absolute value of the AC voltage Vg acquired in step S120 with a predetermined threshold voltage Vα. As a result, if the absolute value of the AC voltage Vg is greater than the threshold voltage Vα, the process proceeds to step S130, and if it is equal to or less than Vα, the process proceeds to step S130.

In step S130, the drive control unit 240 outputs the phase signal Sp from the comparison unit 242 at the H level. If step S130 is performed, it will progress to step S150.

In step S140, the drive control unit 240 outputs the phase signal Sp from the comparison unit 242 at the L level. If step S140 is performed, it will progress to step S150.

In step S150, the drive control unit 240 uses the drive signal generation unit 243, and the phase signal Sp input from the comparison unit 242 in step S130 or S140 is at the H level and is input from the power reception control unit 210. It is determined whether or not the basic drive signal Sr is at the H level. As a result, if both the phase signal Sp and the basic drive signal Sr are at the H level, the process proceeds to step S160, and if at least one of them is at the L level, the process proceeds to step S170.

In step S160, the drive control unit 240 outputs the charge drive signal Sc from the drive signal generation unit 243 to the H level and outputs it. If step S160 is performed, it will progress to step S180.

In step S170, the drive controller 240 outputs the charge drive signal Sc from the drive signal generator 243 to the L level and outputs it. If step S170 is performed, it will progress to step S180.

In step S180, the drive control unit 240 uses the gate drive circuit 244 to generate a gate drive signal according to the charge drive signal Sc input from the drive signal generation unit 243 in step S160 or S170, and the power conversion unit 250. Are respectively output to the gate terminals of the MOS transistors Q1 and Q2. As a result, the MOS transistors Q1 and Q2 are respectively switched according to the gate drive signal, and drive control of the power converter 250 is performed. When the gate drive signal is output in step S180, the process flow in FIG. 4 is terminated, and the drive control process in step S40 or S70 in FIG. 3 is completed.

The power receiving device 200 executes the drive control process described above in the drive control unit 240, thereby switching the MOS transistors Q <b> 1 and Q <b> 2 in the power conversion unit 250 based on the AC current i detected by the AC current detection unit 230. The timing can be changed. Specifically, the drive control unit 240 changes the output of the phase signal Sp in step S130 or step S140 based on the comparison result in step S120. Then, the determination of step S150 is performed based on the output of the phase signal Sp, and the charge drive signal is determined in step S160 or step S170 depending on whether the phase signal Sp and the basic drive signal Sr are both at the H level or not. The output of Sc is changed. In accordance with the output of the charging drive signal Sc thus changed, a gate drive signal is generated in step S180 and output to the MOS transistors Q1 and Q2, respectively. As a result, the timing of the switching operation of the MOS transistors Q1 and Q2 changes according to the phase signal Sp determined by the AC voltage Vg from the AC current detector 230. Therefore, the timing of the switching operation of the MOS transistors Q1 and Q2 can be changed based on the alternating current i detected by the alternating current detector 230.

FIG. 5 is an explanatory diagram of the switching operation of the MOS transistors Q1 and Q2 performed in accordance with the drive control process described in FIG.

As shown in FIG. 5B, when an alternating current i flows through a resonance circuit including the secondary coil L2, the phase advances by 90 ° from the alternating current i, and the alternating voltage Vg synchronized with the alternating current i is alternating current. Output from the current detector 230. Note that the value of the alternating current i in FIG. 5B is positive in the left direction of FIG.

When the absolute value of the AC voltage Vg exceeds the threshold voltage Vα when the basic drive signal Sr for the MOS transistor Q1 is at the H level, a phase angle of 270 ° where Vg = 0 is obtained as shown in FIG. With the timing as a reference point, the MOS transistor Q1 is turned on at a timing delayed by a phase α corresponding to Vα. Similarly, the MOS transistor Q2 is turned on at a timing delayed by the phase α corresponding to Vα from the timing of the phase angle 90 ° where Vg = 0 as a reference point. At this time, these timings are set so that the MOS transistors Q1 and Q2 are turned on while the voltage is zero. On the other hand, the MOS transistors Q1 and Q2 are turned off when the corresponding basic drive signal Sr becomes L level. At this time, these timings are set so that the MOS transistors Q1 and Q2 are turned off while the current is zero.

Between the time when the MOS transistor Q2 is turned off and the time when the MOS transistor Q1 is turned on, the directions of the currents flowing through the MOS transistors Q1 and Q2 change as shown in FIGS. That is, during period A when MOS transistor Q2 is on, no current flows through MOS transistor Q1 in the off state, and current flows from the drain terminal to the source terminal of MOS transistor Q2. Subsequently, in a period B in which the voltage Vo at the connection point O increases immediately after the MOS transistor Q2 is turned off, both the MOS transistors Q1 and Q2 are in the off state, and pass through the parasitic capacitance Cs that each has, so that the MOS transistor Q1. Then, current flows from the source terminal to the drain terminal, and in the MOS transistor Q2, current flows from the drain terminal to the source terminal. This behavior is generally called soft switching, or the Q1 side is called ZCS (Zero Current Switching), and the Q2 side is called ZVS (Zero Voltage Switching).

Thereafter, during a period C from when the voltage Vo at the connection point O becomes constant until the MOS transistor Q1 is turned on and the alternating current i becomes 0, the MOS transistor Q1 has a parasitic diode Ds that passes through the parasitic diode Ds. A current flows from the source terminal to the drain terminal. Thereafter, when the alternating current i becomes positive, a current flows from the drain terminal to the source terminal of the MOS transistor Q1. Subsequently, in a period D until the MOS transistor Q1 is turned off, the MOS transistor Q2 is in an off state and no current flows, and a current flows from the drain terminal to the source terminal of the MOS transistor Q1.

Note that the direction of the current flowing through each of the MOS transistors Q1 and Q2 also changes in the same manner as described above from the time the MOS transistor Q1 is turned off to the time when the MOS transistor Q2 is turned on (periods B 'and C'). At this time, current directions in the periods A ′ to D ′ are opposite to the periods A to D, respectively.

According to the first embodiment of the present invention described above, the following operational effects are obtained.

(1) The power receiving device 200 is wirelessly powered by receiving an alternating magnetic field emitted from the primary coil L1 installed on the ground side. The power receiving device 200 includes a secondary coil L2, a resonance coil Lx and a resonance capacitor Cx that are resonance elements that are connected to the secondary coil L2 and have a resonance circuit having a predetermined resonance frequency together with the secondary coil L2. The coil L2 has an alternating current detection unit 230 that detects an alternating current i flowing in the resonance circuit by receiving an alternating magnetic field, and MOS transistors Q1 and Q2 that are a plurality of switching elements, and each of the MOS transistors Q1 and Q2 performs a switching operation. Thus, a power conversion unit 250 that controls the alternating current i and a drive control unit 240 that controls the switching operation of the MOS transistors Q1 and Q2 are provided. The drive controller 240 changes the timing of the switching operation of the MOS transistors Q1 and Q2 based on the alternating current i detected by the alternating current detector 230. Since it did in this way, the suitable switching operation | movement according to the state of the electric current which flows into the secondary coil L2 of the power receiving apparatus 200 is realizable.

(2) The alternating current detection unit 230 generates an alternating voltage Vg whose frequency and amplitude change according to the alternating current i. The drive control unit 240 changes the timing of the switching operation of the MOS transistors Q1 and Q2 based on the AC voltage Vg. Since it did in this way, the alternating current i can be detected easily and the detection result can be utilized for the timing change of switching operation.

(3) The drive control unit 240 compares the AC voltage Vg with a predetermined threshold voltage Vα (step S120), and changes the timing of the switching operation of the MOS transistors Q1 and Q2 based on the comparison result. Specifically, the power reception device 200 further includes a power reception control unit 210 that generates a basic drive signal Sr corresponding to the frequency f of the current flowing through the primary coil L1. The drive control unit 240 generates a charge drive signal Sc in which the phase of the basic drive signal Sr is changed based on the comparison result between the AC voltage Vg and the threshold voltage Vα (steps S130 to S170), and uses the charge drive signal Sc. Then, the switching operation of the MOS transistors Q1, Q2 is controlled (step S180). Since it did in this way, the timing of switching operation of MOS transistor Q1, Q2 can be changed reliably according to the alternating current i.

-Second Embodiment-
FIG. 6 is a diagram showing a configuration of a wireless power feeding system 1A according to the second embodiment of the present invention.
A wireless power feeding system 1A shown in FIG. 6 is used in wireless power feeding to a vehicle such as an electric vehicle, and includes a power transmission device 100 installed on the ground side in the vicinity of the vehicle and a power receiving device mounted on each vehicle side. 200A, battery 300, load 400, and battery monitoring device 500. Since the power transmission device 100, the battery 300, and the load 400 are the same as those of the wireless power feeding system 1 described in the first embodiment, the power receiving device 200A and the battery monitoring device 500 will be described below.

The power receiving device 200A is the same as the power receiving device 200 in the wireless power feeding system 1 described in the first embodiment, except that a drive control unit 240A is provided instead of the drive control unit 240. The drive control unit 240A is connected to the battery monitoring device 500, acquires the battery voltage Vb from the battery monitoring device 500, and controls the switching operations of the plurality of switching elements included in the power conversion unit 250.

The battery monitoring apparatus 500 is connected to the battery 300 and acquires various information for monitoring the state of the battery 300 from the battery 300. For example, the battery monitoring device 500 detects the voltage of the battery 300 and outputs the detection result to the drive control unit 240A as the battery voltage Vb. In addition, it is determined whether or not the battery 300 is in an overcharged state. If it is determined that the battery 300 is in an overcharged state, a predetermined overcharge signal is output to the drive control unit 240A so that the battery 300 is in an overcharged state. Notify that there is.

Next, details of the power receiving apparatus 200A to which the present invention is applied in the wireless power feeding system 1A of FIG. 6 will be described. FIG. 7 is a diagram illustrating a configuration example of a power receiving device 200A according to the second embodiment of the present invention. The power receiving device 200A is the same as the power receiving device 200 described in the first embodiment, except that the drive control unit 240A includes a comparison unit 242A instead of the comparison unit 242.

The comparison unit 242A receives the AC voltage Vg acquired by the voltage acquisition unit 241 and the battery voltage Vb output from the battery monitoring device 500. The comparison unit 242A sets a threshold voltage α based on the input battery voltage Vb, and compares the input AC voltage Vg with the set threshold voltage Vα. Then, the phase signal Sp corresponding to these comparison results is output to the drive signal generator 243.

FIG. 8 is a diagram showing a processing flow of drive control processing in the power receiving device 200A according to the second embodiment of the present invention.

In Step S110A, the drive control unit 240A acquires the AC voltage Vg from the AC current detection unit 230 and also acquires the battery voltage Vb from the battery monitoring device 500.

In step S111, the drive control unit 240A sets the threshold voltage Vα based on the battery voltage Vb acquired in step S110A. Here, for example, the higher the battery voltage Vb, the higher the threshold voltage Vα is set so that the time during which the MOS transistors Q1 and Q2 are turned on becomes shorter.

If the threshold voltage Vα is set in step S111, the same processing as the processing flow of FIG. 4 described in the first embodiment is performed in subsequent steps S120 and subsequent steps. At this time, in step S120, the threshold voltage Vα set in step S111 is used to compare with the absolute value of the AC voltage Vg. Thereby, the threshold voltage Vα used in the comparison in step S120 is changed based on the battery voltage Vb.

According to the second embodiment of the present invention described above, the following effect (4) is further achieved in addition to the effects (1) to (3) described in the first embodiment.

(4) The power converter 250 is connected to a chargeable / dischargeable battery 300. The drive control unit 240A changes the threshold voltage Vα based on the voltage of the battery 300, that is, the battery voltage Vb (step S111). Since it did in this way, according to the charge condition of the battery 300, switching operation of MOS transistor Q1, Q2 can be performed at an optimal timing.

-Third embodiment-
FIG. 9 is a diagram showing a configuration of a wireless power feeding system 1B according to the third embodiment of the present invention.
A wireless power feeding system 1B shown in FIG. 9 is used for wireless power feeding to a vehicle such as an electric vehicle, and includes a power transmission device 100 installed on the ground side in the vicinity of the vehicle and a power receiving device respectively mounted on the vehicle side. 200B, battery 300, load 400, and battery monitoring device 500. The power transmission device 100, the battery 300, and the load 400 are the same as those of the wireless power supply system 1 described in the first embodiment, and the battery monitoring device 500 is the wireless power supply described in the second embodiment. Since it is the same as that of the system 1A, the power receiving apparatus 200B will be described below.

The power receiving device 200B is the same as the power receiving device 200 in the wireless power feeding system 1 described in the first embodiment, except that a drive control unit 240B is provided instead of the drive control unit 240. The drive control unit 240B is connected to the battery monitoring apparatus 500, and when an overcharge signal is input from the battery monitoring apparatus 500, the power conversion unit 240B is different from the method described in the first embodiment. The switching operation of a plurality of switching elements 250 has is controlled.

Next, details of the power receiving apparatus 200B to which the present invention is applied in the wireless power feeding system 1B of FIG. 9 will be described. FIG. 10 is a diagram illustrating a configuration example of a power receiving device 200B according to the third embodiment of the present invention. The power receiving device 200B is the same as the power receiving device 200 described in the first embodiment, except that the drive control unit 240B includes a drive signal generation unit 243B instead of the drive signal generation unit 243.

In addition to the phase signal Sp from the comparison unit 242 and the basic drive signal Sr from the power reception control unit 210, when the overcharge signal is output from the battery monitoring device 500 to the drive signal generation unit 243B, the overcharge is performed. A signal is input. The drive signal generation unit 243B generates either the charge drive signal Sc or the discharge drive signal Sd according to whether or not an overcharge signal is input, and outputs the generated signal to the gate drive circuit 244.

FIG. 11 is a diagram showing a processing flow of drive control processing in the power receiving device 200B according to the third embodiment of the present invention.

In step S101, the drive control unit 240B determines whether or not an overcharge signal is input from the battery monitoring device 500. If an overcharge signal is input, the process proceeds to step S102. If not input, the process proceeds to step S110. When the processing proceeds to step S110, the drive control unit 240B executes the processing of steps S110 to S180 described in the first embodiment, and ends the processing flow of FIG.

In step S102, the drive control unit 240B stops outputting the charge drive signal Sc from the drive signal generation unit 243B, generates a discharge drive signal Sd instead of the charge drive signal Sc, and outputs it to the gate drive circuit 244. Here, for example, a rectangular wave having a frequency f 'different from the frequency f of the current flowing through the primary coil L1 is output as the discharge drive signal Sd. If step S102 is performed, it will progress to step S180.

When the process proceeds from step S102 to step S180, in step S180, the drive control unit 240 uses the gate drive circuit 244 to generate a gate drive signal corresponding to the discharge drive signal Sd, and the MOS transistor Q1 in the power conversion unit 250 , Output to the gate terminals of Q2. As a result, the DC power of the battery 300 is converted into AC power and output to the resonance circuit including the secondary coil L2, and the AC field is emitted from the secondary coil L2 toward the primary coil L1, thereby discharging the battery 300. To be.

According to the third embodiment of the present invention described above, in addition to the effects (1) to (3) described in the first embodiment, the following effects (5) are further exhibited.

(5) The power converter 250 is connected to a chargeable / dischargeable battery 300. When the battery 300 is in an overcharged state (step S101: Yes), the drive control unit 240B generates a discharge drive signal Sd different from the charge drive signal Sc (step S102), and the MOS transistor Q1 using the discharge drive signal Sd. , Q2 is controlled (step S180). Since it did in this way, when the battery 300 is an overcharge state, the battery 300 can be discharged and an overcharge state can be eliminated.

In each embodiment described above, each component included in each of the drive control units 240, 240A, and 240B may be realized by software executed by a microcomputer or the like, or an FPGA (Field-Programmable Gate Array). It may be realized by hardware such as. These may be used in combination.

In the above embodiments, the wireless power feeding systems 1, 1 </ b> A, and 1 </ b> B used for wireless power feeding to a vehicle such as an electric vehicle have been described. However, the wireless power feeding system is not limited to the wireless power feeding to the vehicle, and is used for other purposes. The present invention may be applied to.

Each embodiment and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Moreover, although various embodiment and the modification were demonstrated above, this invention is not limited to these content. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1, 1A, 1B Wireless power feeding system 100 Power transmission device 110 Power transmission control unit 120 Communication unit 130 AC power supply 140 Power conversion unit 200, 200A, 200B Power reception device 210 Power reception control unit 220 Communication unit 230 AC current detection unit 240, 240A, 240B Drive Control unit 241 Voltage acquisition unit 242, 242A Comparison unit 243, 243B Drive signal generation unit 244 Gate drive circuit 250 Power conversion unit 300 Battery 400 Load 500 Battery monitoring device L1 Primary coil L2 Secondary coil Lx Resonance coil Cx Resonance capacitor Tr Transformer Q1 , Q2 MOS transistor

Claims (6)

A power receiving device that receives an alternating magnetic field emitted from a primary coil installed on the ground side and is wirelessly powered,
A secondary coil;
A resonant element connected to the secondary coil to form a resonant circuit having a predetermined resonant frequency together with the secondary coil;
An alternating current detection unit that detects an alternating current flowing in the resonance circuit when the secondary coil receives the alternating magnetic field;
A power converter that has a plurality of switching elements and controls the alternating current by switching the plurality of switching elements, respectively;
A drive control unit that controls a switching operation of the plurality of switching elements,
The drive control unit is a power receiving device that changes the timing of the switching operation based on the alternating current detected by the alternating current detection unit. The power receiving device according to claim 1,
The alternating current detection unit generates an alternating voltage whose frequency and amplitude change according to the alternating current,
The drive control unit is a power receiving device that changes a timing of the switching operation based on the AC voltage. The power receiving device according to claim 2,
The drive control unit compares the AC voltage with a predetermined threshold voltage, and changes the timing of the switching operation based on the comparison result. The power receiving device according to claim 3,
A power reception control unit that generates a basic drive signal according to the frequency of the current flowing through the primary coil;
The drive control unit generates a drive signal in which a phase of the basic drive signal is changed based on the comparison result, and controls a switching operation of the plurality of switching elements using the drive signal. The power receiving device according to claim 3 or 4,
The power conversion unit is connected to a chargeable / dischargeable battery,
The drive control unit is a power receiving device that changes the threshold voltage based on a voltage of the battery. The power receiving device according to claim 4,
The power conversion unit is connected to a chargeable / dischargeable battery,
The drive control unit generates a second drive signal different from the drive signal when the battery is in an overcharged state, and controls a switching operation of the plurality of switching elements using the second drive signal. Power receiving device.

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